I'm hitting the 4GB limit of FAT32 on USB drives more and more often. However, being able to unplug the device without unmounting it first is a must have for me. I've noticed exFAT recently, however I couldn't find any info on whether drives formatted with exFAT can be unplugged safely without unmounting.

Any flash drive must be unmounted first. Flash is quite notorious for causing widespread data damage if unplugged while still writing, and the underlying physical process may take up to 2 seconds (especially with cheap MLC flash). This corruption is due to the fact that flash internally uses 128kB+ blocks, and remaps those rather randomly for "wear leveling purposes". You could corrupt 256 files that way.
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MSaltersAug 10 '11 at 1:06

How/why is it safer to remove a FAT drive versus an NTFS drive without unmounting?
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BreakthroughJun 30 '11 at 17:13

It's true I didn't give much justification for that. As one of the other answers stated, NTFS often buffers writes which can lead to uncommitted changes when one saves a file.
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jweedeJul 1 '11 at 3:03

Not really specific to exFAT but:
I'd say it's NEVER really safe to unplug an USB drive without unmounting it first. At least when you've written stuff to the disk. As long as you're only reading, unplugging without unmounting can do no harm, but the moment you've actually written something onto the disk, you have to unmount it for the buffers to be flushed (It's possible that not everything is written yet to the disk).
If you wait long enough, they will be flushed, and it would be safe again to unplug without unmounting.

I believe you are giving a *nix answer to what was intended as a Windows question. (At least, Windows does not generally behave in the manner you describe with FAT filesystems, whereas Linux does.)
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SamBJan 25 '11 at 0:13

@SamB: What do you mean? This answer wasn't really meant to be specific to any platform... but I know it's like this on Windows.
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fretjeFeb 1 '11 at 10:27

NTFS is not meant for removable drives. exFAT was designed for this, but keep this in mind: FAT12/FAT16 & FAT32 have 2 FAT's, they flip-flop. exFAT has one FAT, and if it gets corrupted, you're screwed. In a later release of exFAT there will be TexFAT (Transaction Safe exFAT) where there will be 2 FATs and 2 allocation bit maps. It will be safer.

But not unmounting is a risk, but less of a risk than NTFS because NTFS is lazy write and doesn't write everything out immediately, it bussers it.